MOLLUSCA. 647 



Remarks. This species has a rather long range in the New 

 Jersey Cretaceous beds, but it is most characteristically a member 

 of the Merchantville fauna. It reaches its largest size at this 

 horizon, those of the higher formations rarely exceeding 50 mm. 

 in length, and usually being even smaller than this. 



Formation and locality. Merchantville clay-marl, near Mata- 

 wan (ioo 4 , 101), near Jamesburg (140), Lenola (163) ; Wood- 

 bury clay, Crosswicks (168), near Haddonfield (164) ; Wenonah 

 sand, near Marlboro (130) ; Navesink marl, Atlantic Highlands 

 (108), near Crawfords Corner (i26 7 ), Crosswicks Creek (195) ; 

 Red Bank sand, Red Bank (116). 



Geographic distribution. New Jersey, Alabama, Mississippi, 

 Texas. 



Panopea elliptica Whitfield. 

 Plate LXXIIL, Figs. 1-2. 



1886. Panopea elliptica. Whitf., Pal. N. J., vol. i (Monog. U. S. 

 G. S., vol. 9), p. 219, pi. 28, figs. 24-25. 



Description. The type specimen of this species is too imperfect 

 to allow accurate measurements, but the dimensions of the best 

 preserved specimen which has been observed are: length, 62.5 

 mm.; height, 38 mm.; thickness, 27.5 mm. Shell subelliptical in 

 outline. Hinge-line long and nearly straight; anterior margin 

 rounded, the greatest extension at or above the mid-height of the 

 shell ; basal margin convex, curving upward in front and behind 

 into the anterior and posterior margins ; posterior margin more 

 broadly rounded than the anterior, the greatest extension at the 

 middle. Beaks broad and moderately prominent, pointed for- 

 ward ; the anterior umbonal slope more abrupt than the posterior. 

 Valves rather strongly convex, with an indefinite, rounded, an- 

 terior umbonal ridge ; posterior umbonal ridge obsolete. Surface 

 of the cast marked by rather strong, more or less irregular, con- 

 centric undulations. 



Remarks. This species is known only from very imperfect in- 

 ternal casts, the most perfect of which was selected by Whitfield 

 as the type. In his interpretation of it, the author of the species 



